A text buffer stores an arrangement of characters for input to a picture surface depending on character code and position information in a character signal generator. When a picture signal is output, such character codes are sequentially read and converted into the picture signal. In the prior art, for example, as shown in FIG. 1, the character codes have been arranged bi-dimensionally for storing in the memory corresponding to the arrangement of characters to be output for simplification of position information processing. Namely, the buffer memory is divided into M-region in the direction X in unit of character code (for example, 8 bits), this is arranged in N rows in the direction Y to form the M.times.N matrix. The character codes are arranged and stored within the M.times.N matrix corresponding to the character arrangement on the output picture.
A system where the character codes to be stored in the text buffer memory correspond to the character arrangement on the output picture is further capable of alleviating the task of software when the character code is converted to a dot matrix type picture signal because the memory address in the text buffer corresponds to the locations of characters on the output picture and can be generally employed for an apparatus such as a laser beam dot printer which is required to output the picture signal at a high speed.
However, this method is restricted in the number of characters to be stored in each row in the direction X and therefore has a disadvantage in that the number of characters to be stored in a row cannot be increased even when characters to be output become small in size. Moreover, this method has also a disadvantage in that, even when the character codes to be stored in each row in the direction X is less than the given number of divisions (M), a row must be completed by assigning the space code to the remaining storage area and accordingly the storage area is used inefficiently as compared with the number of characters stored actually and thereby efficiency in the use of memory is deteriorated.
Accordingly, the application profile of an existing text buffer is not sufficient for a current printer which processes a large amount of data at a high speed and is required to meet the versatility required by such printers, such as conversion in size of characters.